Catalytic cracking processes in which hydrocarbonaceous oil is converted to lower boiling hydrocarbon products in the presence of cracking catalysts are well known. These processes involve contamination of catalyst with carbon and high-boiling hydrocarbon. In order to remove the contaminants, the catalyst is subjected to regeneration at higher temperatures before it is returned to the cracking zone. Generally, during the process of regeneration, the zeolite component of the catalysts loses a substantial portion of its crystallinity and activity. Their catalytic activity is reduced rapidly. There had been a lot of research done in this field for improving the stability of the catalyst. There are many literature in the prior art which teaches the attrition resistant zeolite based catalysts but there has been a very less information or knowledge of aluminium phosphate binder based zeolite catalyst which are stable and cracks hydrocarbon molecules selectively to produce light olefins.
Following patents illustrate prior art processes and compositions which are different from present invention with respect to composition, process and performance.
U.S. Pat. No. 5,286,369 discloses aluminium phosphate binder for binding various zeolites, prepared by reaction between aluminium nitrate and phosphoric acid. However, the nitric acid which is by product of binder production, affects activity and selectivity of the finished catalyst product, though it possess acceptable Attrition Index.
U.S. Pat. No. 3,847,793 discloses a process for conversion of hydrocarbons with a dual cracking component catalyst comprising ZSM-5 zeolite based catalyst and large pore zeolite based catalyst.
U.S. Pat. No. 6,258,257 discloses a process for producing polypropylene from C3 olefins by a two-stage fluid catalytic cracking process having two types of catalysts made from zeolites of large pore and medium pore.
U.S. Pat. No. 6,137,022 discloses a process of making an olefin product from an oxygenated feedstock by contacting the feedstock in a reaction zone containing 15 volume percent or less of a catalyst, preferably a catalyst comprising a silica-alumina-phosphate molecular sieve.
EP0167325A relates to higher make-up of catalyst that may contain 2 or 3 times the amount of ZSM-5 sought for the equilibrium catalyst.
U.S. Pat. No. 4,309,280 describes a process for maximizing of LPG by adding very small amounts of powdered, neat ZSM-5 catalyst, characterized by a particle size below 5 microns to the FCC catalyst inventory.
U.S. Pat. No. 4,784,745 relates to a catalyst and a process for enhancing octane number of gasoline, wherein said shape-selective zeolite is selected from the group having the structure of ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-34, ZSM-35, ZSM-38, ZSM-48, ZSM-50, TMA Offretite and Erionite.
U.S. Pat. No. 4,867,863 deals with a Resid catalytic cracking process utilizing ZSM-5 for increased gasoline octane.
U.S. Pat. No. 5,039,640 refers to a catalyst composition comprising of large pore crystalline molecular sieve component and an MCM-22 zeolite for catalytic cracking of a hydrocarbon oil to provide a product of increased octane number and increased C5+ gasoline content.
U.S. Pat. No. 5,055,437 deals with multi-component catalyst mixture having Ga in ZSM-5 and process for catalytic cracking of heavy hydrocarbon feed to lighter products.
U.S. Pat. No. 5,190,902 and Canadian patent i.e., CA2156607A1 discloses the processes for the preparation of attrition resistant binder particles by spray drying of clay phosphate slurry and ZSM-5 zeolite with adjusted extreme pH conditions.
U.S. Pat. No. 5,348,643 relates to a process for converting feedstock hydrocarbon compounds over a catalyst composition comprising clay and a zeolite component, at least one of which has been treated with a phosphorus-containing compound, which is spray dried at a low pH, to produce high octane gasoline and increased lower olefins, especially propylene and butylene
U.S. Pat. No. 5,707,442A discloses novel aluminium phosphates, in particular amorphous aluminium phosphate powders having a BET specific surface no greater than 25 m2/g, well suited as binders/hardeners or for the production of ceramic shaped articles, are prepared by reacting at least one aluminium compound, e.g., an aluminium oxide, hydroxide or oxyhydroxide, with phosphoric acid or an aluminium phosphate, e.g., an acid aluminium orthophosphate, in a liquid reaction medium devoid of inorganic acid anions other than of phosphoric acid, and then spray- or freeze-drying the suspension thus obtained.
U.S. Pat. No. 5,846,402 relates to a process for selective catalytic cracking of a petroleum-based feedstock to produce a product having a high yield of liquefied petroleum gas (LPG) and light olefins having 3 to 4 carbons.
U.S. Pat. No. 5,997,728, refers to a process for cracking of heavy feed in an FCC unit, to enhance light olefins, without excessive production of aromatics, or loss of gasoline yield with large amounts of shape selective cracking additive preferably at least 10 wt % additive, of 12-40% ZSM-5 on an amorphous support, equivalent to more than 3.0 wt % ZSM-5 crystal circulating with equilibrium catalyst.
U.S. Pat. No. 6,613,710 deals with a process for preparing bi-functional catalyst comprising of molecular sieves, modified clay and semi-basic alumina for effective cracking of high boiling petroleum feedstock to provide simultaneously, enhanced yields of Liquefied Petroleum Gas (LPG) and reduction of undesirable bottoms.
U.S. Pat. No. 6,677,263 discloses a catalytic promoter comprising of 5-65 wt % of modified HZSM-5 zeolite with Zn, P, Ga, Al, Ni and rare earth elements in an amount 0.01-10.37 wt % based on total weight of HZSM-5 zeolite to increase gasoline octane number and an increased lower olefin yield.
U.S. Pat. No. 7,517,827 teaches preparation of cracking catalyst composition having high selectivity towards production light olefins such as LPG, propylene etc. achieved through treating the zeolite with sodium free basic compound with or without phosphate. Though the catalyst provides activity and selectivity towards light olefins but it lacks attrition resistance.
U.S. Pat. No. 6,080,303 teaches a process for improving the catalytic activity of small and medium pore acidic zeolite catalyst which comprises the steps of treating a zeolite with a phosphorus compound to form phosphorus treated zeolite and combining the phosphorus treated zeolite with aluminium phosphate.
Although research is being done on stability of catalyst and to enhance the attrition resistant properties of the cracking catalyst, however none of the prior arts discloses the catalyst possessing the properties such as enhanced attrition resistant properties as well as cracking of hydrocarbon molecules selectively to produce light olefins.
Hence, there has always been a demand of development of process that can address the drawbacks of the prior arts.